Dual loop antenna



June 25, 1968 s. R. GLIMVALVL 3,390,394

DUAL LOOP ANTENNA Filed Oct. 2, 1964 I I 41 I F I [4 i 18 I I i I I 1 II v 1 1 ISM: 13 :I i J l9'- I I I I I I I l l I I i T- -23 F-24 I 2o--25 /iI EI H II II II If Mm I FEH IO H1O A 3 A B INVENTOR SVEN REINHOLDGLIMVALL ATTORNEYS United States Patent 3,390,394 DUAL LOOP ANTENNA SvenReinhold Glimvall, Malmo, Sweden, assignor to Gote Sigvard Gustafson,Malmo, Sweden Filed Oct. 2, 1964, Ser. No. 401,127 Claims priority,application Sweden, Oct. 4, 1963, 10,866/63 3 Claims. (Cl. 343-742)ABSTRACT OF THE DISCLOSURE The invention relates to an antenna, moreparticularly a TV antenna, of small dimensions and large band width andincludes a continuous conductor placed in two rectangular loops, andmetal powder tubes which are positioned around three of the long sidesof the loops to reduce the Q-value of the antenna, and a plasticcovering enclosing the conductor and the metal powder tubes.

The present invention relates to an antenna including a continuousconductor placed in two substantially rectangular loops.

To obtain the best possible results in transmitting or receivingelectromagnetic waves the antennas employed must have a certaindimension adapted to the wave length in question, and this dimension asa rule is not shorter than half the wave length at horizontal antennasor a quarter of the wave length at vertical antennas. At very short wavelengths there are usually employed antennas having auxiliary elements inthe form of directors and reflectors. Prior-art antennas thus generallyhave considerable dimensions, which is disadvantageous in many respects.Further, such antennas are rather selective, and their efiiciencytherefore considerably decreases when one goes beyond the wave lengthfor which the antenna is adapted, which particularly applies to antennashaving auxiliary elements. For the reception of e.g., televisionprograms is therefore required in principle one antenna for eachchannel, which in places Where two, three or more programs can bereceived results in a large and heavy antenna structure and, if thisstruc ture is placed on a roof it will expose the fastening devices andthe roof-truss to heavy stresses. Such antenna arrangements besides arevery unsightly, particularly in densely populated areas.

The invention has for its object to eliminate these disadvantages and toprovide a very small, lightweight and broadband antenna. This isrealized in that the long sides of the rectangular loops are parallelwith each other and coplanar and three of said loops are enclosed inmetal powder tubes.

These and further features of the invention will become apparent fromthe following description in which reference is made to the accompanyingdrawing illusstrating a preferred form of the invention. In the drawing:

FIG. 1 is a diagrammatical view of the antenna according to theinvention;

FIGS. 2 and 3 are views of difierent ways of feeding the antenna.

In the drawing, designates a continuous conductor which is placed in twosubstantially rectangular loops consisting of parts 13, 14, 15, 16 and17, 18, 19, 20, respectively, which are coplanar and of which parts 13and 17 extend in parallel with and are closely spaced relative to oneanother. The parts 13 and 20 of the conductor are connected viaterminals 12 and 11 to the braid and the inner conductor, respectively,of a coaxial cable 21. Around the parts 15, 17 and 19 are braids 22, 23,and 24, respectively, in the form of tubes made of metal powder whichare insulated "Ice from the conductor and from each other. The conductor10 and the tubes 22, 23, 24 thereon are enclosed in a sheath 25 ofplastic material consisting of a central tube in which parts -13 and 17are enclosed, two tubular portions projecting at right angles from theupper end of the tube in opposite directions and containing parts 14 and18, respectively, two tubular portions extending from the ends of thefirst-mentioned tubular portions at right angles thereto and in parallelwith the central tube and accommodating part 15 and braid 22 andrespectively part 19 and braid 24, and finally two tubular portionsextending from the ends of the last-mentioned tubular portions at rightangles thereto and to the central tube and connected to said centraltube, part 16 and part 20, respectively, of the conductor being enclosedin said final tubular portions. All conductor parts and braids may beconveniently secured and, as the case may be, centered in the varioustubular portions of the sheath.

The feed line used preferably is a coaxial cable having an impedance of709; however, also a band cable having an impedfance of 3009 may beemployed. The coaxial cable may be connected [as shown in FIG. 1, inwhich case, however, the standing wave ratio will be rather high, forwhich reason the connection should preferably be efiected as shown inFIGS. 2. and 3. With the connection utilized in FIG. 2 one end of theconductor 12 is free while a resistor R is connected to the other end.The inner conductor of the coaxial cable is connected to the terminal 'Band the braid of the coaxial cable to the terminal A. With the manner offeeding according to FIG. 3 the two ends of the conductor 12 areconnected together and to the terminal B to which there is alsoconnected a resistor R which on the opposite side is connected to theterminal A. The coaxial cable is connected with its inner conductor to Band the braid is connected to A. In tests carried out with theembodiment according to FIGS. 2 and 3 using a 709 coaxial cable and aresistance value R=10 Nl the standing wave ratio at frequencies between50 mHz. and 200 mHz. never exc eded 1:2.

An antenna according to the invention particularly dimensioned fortelevision reception and 25 x 25 cm. in size, which was connected to acoaxial cable having an impedance of 709 and which was fixedly arranged,gave a perfect reception on channels 4 and 10 and an acceptablereception on channels 2, 6, 7 and 9. In the latter case when thetransmitting stations were located at considerable distances theantenna, however, had to be rotated to a certain position in relation tothe transmitting station to obtain the highest possible rece-ptionquality. By reason of its high sensibility the antenna can therefore beused for the reception of signals coming from all directions, providedthat their strength is not too low, while at low signal strengths theantenna like the prior-art antennas has to be set in a certain positionin relation to each transmitting station.

The invention thus provides an antenna which can be utilized with goodefliciency for a considerable range of frequencies. Furthermore, theantenna is simple, can be mounted indoors or outdoors with simple andcheap means and finally can be manufactured to a price considerablylower than that of conventional antennas.

The invention is not limited to the forms described above and shown inthe drawing but can be modified in many ways within the scope of theappendant claims.

What I claim and desire to secure by Letters Patent is:

1. A large bandwidth antenna including a continuous conductor extendingin two rectangular loops with the long sides thereof parallel andcoplanar with each other, a first terminal, the conductor extending fromsaid first terminal merging into one short side of the first rectangularloop and after completion of said loop merging into one short side ofthe second loop, and completing said second loop, a second terminal onsaid conductor at the end of said second loop, tubes of metal powderaround all the long sides of said loops except the one adjacent thesecond terminal, and a plastic covering enclosing said loops and saidtubes, the terminals being accessible through said covering for theconnection of a feed line thereto.

2. A large bandwidth antenna including a continuous conductor extendingin two rectangular loops with th long sides thereof parallel andcoplanar with each other, the conductor extending into one short side ofthe first rectangular loop and after completion of said loop merging inoone short side of the second loop and completing said second loop, theends of said loop being connected, tubes of metal powder around all thelong sides of said loop except the second side adjacent the end of thesecond loop, a first terminal connected to the connection between theends of the loop, a resistor having one end connected between said firstterminal and the connection between the ends of the loop, a secondterminal at the other end of said resistor, and a plastic coveringenclosing said loops and said tubes, the terminals being accessiblethrough sa d covering for the connection of a feed line to saidterminals.

3. A large bandwidth antenna including a continuous conductor extendingin two rectangular loops with the long sides thereof parallel andcoplanar with each other, the conductor extending into one short side ofthe first rectangular loop and after completion of said loop merginginto one short side of the second loop and completing said second loop,tubes of metal powder around all the long sides of said loops except thesecond side adjacent the end of the second loop, a first terminalconnected to the end of said second loop, a resistor having one endconnected between said first terminal and the end of said second loop, asecond terminal at the other end of said resistor, the end of saidconductor starting said first loop being left unconnected, and a plasticcovering enclosing said loops and said tubes, the terminals beingaccessible through said covering for the connection of a feed line tosaid terminals.

References Cited UNITED STATES PATENTS 1,296,177 3/1919 Franklin 3438671,731,992 10/1929 Van Bronk 343855 X 2,521,550 9/1950 Smith 3437422,537,191 1/1951 Moore 343742 FOREIGN PATENTS 538,388 3/1957 Canada.

OTHER REFERENCES Screened Frame Aerials, Wireless World, June 1940, pp.304308.

HERMAN KARL SAALBACH, Primary Examiner.

PAUL GENSLER, Assistant Examiner.

